This invention pertains generally to radio frequency (R.F.) oscillators, and particularly to R.F. oscillators using solid state elements such as IMPATT diodes.
It is known in the art that great care must be taken in the design, construction and operation of R.F. oscillators using IMPATT diodes if desired results are to be attained. In particular, it is necessary that great care be taken to control the operational characteristics of the IMPATT diode (or diodes) used in any R.F. oscillator. Thus, attempts have been made to maintain the temperature of the junction in an IMPATT diode at a constant value regardless of ambient temperature or duty cycle. For example, it is well known to provide a conventional temperature-controlled housing so that changes in ambient temperature are of no moment or to provide (when pulsed operation is desired) a bias current during interpulse intervals that is sufficient to maintain the temperature of the junction at a temperature slightly less than the temperature of the junction during each pulse.
While the just-mentioned techniques are of value in that either, or both, may be used to extend the range of ambient temperatures and duty cycles in which IMPATT diodes may be satisfactorily operated, both techniques require the expenditure of power that does not directly contribute to the production of R.F. oscillations.
Another deficiency of known techniques for controlling an IMPATT diode in an R.F. oscillator derives from the fact that the temperature at the junction of an IMPATT diode ordinarily rises during operation. Thus, in an application such as an active seeker in a guided missile, it is common practice to operate the IMPATT diode at a lower than optimum power level so that the chance of catastrophic failure is reduced to an acceptable level. Obviously, the maximum range for guidance is reduced when the actual power level of the IMPATT diode is lower than optimum.